Understanding the drivers of woody plant diversity in urban parks in a snow climate city of China

Urban parks are an important part of urban ecosystems and play an important role in biodiversity conservation.However,it is still unclear how park characteristics aff ect plant diversity which could hinder the conservation of urban biodiversity due to the ineff ective design of urban parks.The diversity of woody plants in 33 parks of Changchun,China,was measured with plot measurements and linked with urban park characteristics(e.g.,size and age of the park)to uncover the relationship between them.The results show that urban woody plant species were abundant,with 98 species belonging to 51 genera and 26 families in the snow climate city of Changchun.The variation in woody plant diversity was largely explained by internal patch characteristics(e.g.,size,age,shape),and external factors surrounding the park(e.g.,land use type and socioeconomic level)accounted for only 16.0%in our study.For internal patch characteristics,older urban parks with larger areas demonstrated a richer level of plant diversity and increased nonlinearly with increasing park area.The threshold size signifi cantly aff ecting plant diversity variation was approximately 30 ha.Plant diversity had positive linear relationships with the ages of urban parks,supporting the legacy eff ect.In addition,woody plant diversity nonlinearly decreased with increasing park shape index,which suggested that the plant diversity could also be increased by optimizing the park shape.Regarding the external factors surrounding parks,the spatial distribution of woody plant diversity varied greatly from the urban center to the suburbs.House prices around the park had positive linear relationships with woody plant diversity in parks,supporting the luxury eff ect.However,building and road proportions,and green space proportion had no relationship with plant diversity in parks.This study can provide a robust reference for enriching plant diversity in urban parks,thus improving the development of urban sustainable cities.

The spatial-temporal pattern and influencing factors of negative air ions in urban forests, Shanghai, China

Negative air ions are natural components of the air we breathe Forests are the main continuous natural source of negative air ions （NAI）. The spatio-temporal patterns of negative air ions were explored in Shanghai, based on monthly monitoring in 15 parks from March 2009 to February 2010. In each park, sampling sites were selected in forests and open spaces. The annual variation in negative air ion concentrations （NAIC） showed peak values from June to October and minimum values from December to January. NAIC were highest in summer and autumn, intermediate in spring, and lowest in winter. During spring and summer, NAIC in open spaces were significantly higher in rural areas than those in suburban areas. However, there were no significant differences in NAIC at forest sites among seasons. For open spaces, total suspended particles （TSP） were the dominant determining factor of NAIC in sum- mer, and air temperature and air humidity were the dominant determining factors of NAIC in spring, which were tightly correlated with Shanghai＇s ongoing urbanization and its impacts on the environment. R is suggested that urbanization could induce variation in NAIC along the urban-rural gradient, but that may not change the temporal variation pattern. Fur- thermore, the effects of urbanization on NAIC were limited in non-vegetated or less-vegetated sites, such as open spaces, but not in well-vegetated areas, such as urban forests. Therefore, we suggest that urban greening, especially urban forest, has significant resistance to theeffect of urbanization on NAIC.

An interactive simulation model of urban ecosystem and its implementation

An interactive simulation model is established based on the methodology of 'sensitivity model' (SM) during the cooperative research process between the founders of SM and the authors. And the conceptual framework of SM is developed into the interactively qualitative and quantitative simulation model presented in this paper, which makes it possible to break down a complex urban ecosystem into simple and visual quantitative or qualitative relationships between the factors. By studying the dynamic responses of the system to the changes of the inputs and parameters of the model, future trends in urban development can be predicted and strategies formulated. The whole process is realized on micro-computer in the course of man-computer interaction. Its potential use is shown in a case of Tianjin City.

Seasonal co-occurrence patterns of bacteria and eukaryotic phytoplankton and the ecological response in urban aquatic ecosystem

Microorganisms play a key role in aquatic ecosystems.Recent studies show that keystone taxa in microbial community could change the community structure and function.However,most previous studies focus on abundant taxa but neglected low abundant ones.To clarify the seasonal variation of bacterial and microalgal communities and understand their synergistic adaptation to diff erent environmental factors,we studied the bacterial and eukaryotic phytoplankton communities in Fenhe River that runs through Taiyuan City,central China,and their seasonal co-occurrence patterns using 16S and 18S rDNA sequencing.Results indicate that positive interaction of eukaryotic phytoplankton network was more active than negative one except winter,indicating that the cooperation(symbiotic phenomenon in which phytoplankton are interdependent and mutually benefi cial)among them could improve the adaption of microbial community to the local environmental changes and maintain the stability of microbial network.The main genera that identifi ed as keystone taxa in bacterial network were Salinivibrio and Sphingopyxis of Proteobacteria and they could respond to the variation of nitrite and make use of it,while those that identifi ed as keystone taxa in eukaryotic phytoplankton network were Pseudoschroederia and Nannochloris,and they were more susceptible to nitrate and phosphate.Mychonastes and Cryptomonas were closely related to water temperature.However,the loss of the co-occurrence by environmental factor changes aff ected the stability of network structure.This study provided a reference for analyzing relationship between bacteria and eukaryotic phytoplankton and revealing potential importance of keystone taxa in similar ecological domains in carbon,nitrogen,and phosphorus dynamics.

Balanced Consideration of Urban Park Green Space to Provide Services and Disservices

Ecosystem services(ES),the benefits of ecosystem function and structure to human well⁃being,have been receiving continued attention from international community since the publication of the millennium ecosystem assessment(MA).While humans enjoy all kinds of services provided by the ecosystem,they are also adversely affected by the services provided by the ecosystem,which are called ecosystem disservices(EDS).Based on EDS related research,this paper expounds the EDS concept and connotation to urban park green space as the research object,defines the concept and classification of urban park green space ecosystem disservices(PEDS),and introduces the influencing factors of the listed examples of urban PEDSs.It also discusses equilibrium relationship of the urban park green space service and disservice,and summarizes the research on urban PEDS to improve the meaning of human well⁃being.Finally,it points out the factors that should be considered in the planning,design,management,and maintenance of future urban park green space.

Hallmark of a Resilient City: Adoption of Green Infrastructure in African Cities

Dynamic urbanization of African cities has created development trajectories that face systemic challenges in the provision of sustainable and ecologically resilient urban environments. The specific challenges include extensive unregulated growth with informal settlements reflecting poor service levels and high poverty indices, inadequacy in provision of basic services in health, water, housing, transport and communication infrastructure, high reliance on biomass fuels, exposure to environmental stress and implausible climate change coping and mitigation mechanisms among others. Review of extensive literature and synthesis of existing bodies of knowledge on the ecological and management perspectives of urban environments revealed many gaps and understanding of urban transformation processes. The purpose of this review was to contextualize credible pathways for optimization of both ecosystem goods and services from green urban landscapes (Green infrastructure) and non-green infrastructure to ensure sustainable and ecologically resilient urban environments. Attempts were made to rationalize and validate through discussions the benefits of managed urban ecosystems for African cities. On the basis of the evidence from the literature, it is concluded that urban development trajectories that do not embrace multifaceted approaches that deliberately retain and maintain green infrastructure in the urban environment may not be cost-effective. It is recommended that systematic integration of urban forestry concepts in urban planning that involves communities, local and national governments, business entrepreneurs and public and private research institutions provides tenable frameworks for addressing current and future challenges of urbanization in Africa.

Ecological assessment of cities-procedure and a case study

This paper discusses the scientific background and content of the ecological assessment of cities, and takes Boda, a new town in Xinjiang province, China, as a case study.

The Practice Strategy of Construction of Ecological Garden City in China: A Case Study of Action of “Xuchang Being Full of Green” in Xuchang City

Starting from the purpose and current situation of the implementation of action of "Xuchang being full of green",this study analyzed the problems existing in the implementation of action of "Xuchang being full of green" and discussed the implementation plan of action of "Xuchang being full of green" from two aspects of macro strategy and node promotion strategy,hoping to promote the construction of ecological garden cities in Xuchang and other cities in China.

Sustainability analysis of the urban ecosystem in Guangzhou City based on information entropy between 2004 and 2010

The urban ecosystem possesses dissipating structures that can absorb substances and energy from the external environment and export products and wastes to maintain order within the system. Given these circumstances, this paper analyzed the ability of the urban ecosystem in Guangzhou City to sustain development from the perspective of entropy. The research was carried out in three steps. First, an evaluation index system that considers the ability of the urban ecosystem for sustainable development was formed based on the struc- tures and functions of the urban ecosystem and the change in the entropy of the urban so- cioeconomic ecosystem. Second, the sustainable development ability assessment model for the urban ecosystem was built using information entropy. Last, by combining the time series variation of the evaluation indicators with the entropy weights, this paper analyzed the influ- ence of the combined factors on the sustainable development ability of the urban ecosystem in Guangzhou and suggested some measures to promote the sustainable development of the urban ecosystem in Guangzhou. The conclusions of this study can be summarized as follows： （1） The urban ecosystem has developed in an orderly and healthy direction, with effective control over the urban environmental pollution problems in Guangzhou between 2004 and 2010. （2） The sustainable development ability of the urban ecosystem had been on an up- ward trend in Guangzhou during the study period. The ability of the natural urban ecosystem to support the urban socioeconomic ecosystem increased continuously, and the improved ecoenvironment enhanced the harmony and vitality of the urban ecosystem in Guangzhou.

Nitrogen pollution and source identification of urban ecosystem surface water in Beijing

Nitrogen contamination of surface water is a worldwide environmental problem with intensive agricul- ture and high population densities. We assessed the spatial and seasonal variation in concentrations of total nitrogen and different nitrogen species present in surface-water in Beijing, China. Also, chemical （NO3-N/C1-） and isotopic （615Nnitrate） indicators were used to identify nitrate sources. The results showed that, during 2009 and 2010, nitrate nitrogen concentrations ranged from 0.7 to 7.6 mg· L^-1, ammonium nitrogen from 0. I to 3.4 mg· L^-1, and total nitrogen from 2.4 to 17.0mg· L^-1. Inorganic nitrogen accounted for between 60 and 100% of total nitrogen at the ten monitoring sites. Nitrate nitrogen, ammonium nitrogen, and total nitrogen concentrations at the 2 downstream monitoring sites in south-eastern Beijing were significantly higher than those at the other eight upstream monitoring sites （P 〈 0.01）. Examination of seasonal variation showed that there was a significant inverse relationship between nitrate nitrogen concentrations and precipitation, and that nitrate nitrogen concentrations peaked in the dry seasons. The information given by the 15Nnitrate values and nitrate nitrogen concentrations, combined with the NO3-N/C1- ratio distribution, showed that domestic sewage was the major source of nitrate in Beijing. Methods to control and reduce sewage pollution are urgently needed to help manage surface water quality in Beijing.

Big data and the future of urban ecology:From the concept to results

Urban ecology is experiencing the third paradigm shift.To understand the interactions between the social system and the natural system in the city across time and space,and to provide theories and solutions to sustainable urban development are essential tasks for urban ecology in the next decade.Big data can play a crucial role in future urban ecology studies due to the interdisciplinary nature of urban ecology,the fact that cities are factories of big data,and the new insights gained by using big data in studies.Nevertheless,to translate big data from a concept to research results that can guide planning,policymaking,and management of cities,we need to overcome multiple challenges existing in the theoretical framework,data acquisition,and analytic methods.Urban ecologists should enhance the collaboration with the data scientists to increase the application of big data in studies of urban biodiversity,urban ecosystem services and human wellbeing,and processes of urban ecosystems.

Dispersal of invasive Phytolacca americana seeds by birds in an urban garden in China

Although seed dispersal is a key process determining the regeneration and spread of invasive plant populations,few studies have explicitly addressed the link between dispersal vector behavior and seedling recruitment to gain insight into the invasion process within an urban garden context.We evaluated the role of bird vectors in the dispersal of pokeweed(Phytolacca americana),a North American herb that is invasive in urban gardens in China.Fruiting P.americana attracted both generalist and specialist bird species that fed on and dispersed its seeds.The generalist species Pycnonotus sinensis and Urocissa erythrorhyncha were the most frequent dispersers.Seedling numbers of P.americana were strongly associated with the perching behavior of frugivorous birds.If newly recruited bird species use seedling-safe perching sites,the P.americana will regenerate faster,which would enhance its invasive potential.Based on our observations,we conclude that the 2 main bird vectors,P.sinensis and U.erythrorhyncha,provide potential effective dispersal agents for P.americana.Our results highlight the role of native birds in seed dispersal of invasive plants in urban gardens.

Spatially explicit urban green indicators for characterizing vegetation cover and public green space proximity: a case study on Brussels, Belgium

Cities often have a substantial green infrastructure,which provides local ecosystem services that improve the quality of life of urban residents.These services should be explicitly addressed in urban development policies,and areas with insufficient vegetation and limited access to public green spaces should be identified.This paper presents two spatially explicit urban green indicators that are derived using remote sensing imagery,freely available map data and spatial analysis tools from open source geospatial libraries and commercial software.The first indicator represents proportional green cover(public as well as private)in the vicinity of each building within a city.The second indicator quantifies the proximity of public green spaces as walking distances from buildings to actual park entrances.A dasymetric mapping approach was used to take spatial variations in population density into account.This allows representing the indicators from the perspective of citizens instead of buildings,which may be more meaningful for deriving statistics at city level or at the level of neighbourhoods or administrative zones.The potential use of these indicators in a planning context is discussed on a case study carried out for the city of Brussels,Belgium.

Urban Ecosystem Prediction and Comprehensive Evaluation Ideology

In the light of the study of domestic and foreign ur-ban ecosystem,this article puts forward a set of ideological systemsfor the forecast,evaluation and tactic,and conducts initial primaryexploration of its forecast and evaluation methods.

Rapid assessment checklist for green roof ecosystem services in Bangkok,Thailand

Background:A green roof is a man-made ecosystem created when a rooftop is covered with substrate and vegetation.Although green roof ecosystems(GREs)are able to provide ecosystem services,there is currently no assessment tool available to specifically evaluate this.Therefore,the aim of this study was to develop a rapid assessment checklist(RAC)to assess GRE services(GRES),which was developed and tested on 10 green roofs in Bangkok,Thailand.Results:The RAC consisted of 46 proxy indicators(33 qualitative and 13 quantitative indicators)encompassing various aspects of GRESs.The GRES values or scores varied according to structural differences in the green roofs.The average score(from a maximum of 100)of total ecosystem services was 61±7,which could be inferred as a good performance in ecosystem service provision.The highest scores were obtained from the regulating services at 68±7.The lowest average score was 53±11 from the provisioning services.Conclusions:The RAC was able to evaluate the levels of GRES provided by the selected green roofs,enabling the meaningful comparison of their potential capability to provide GRES.Therefore,this RAC could be an innovative tool for evaluation of four categories of GRES.

Research strategy for constructing a green infrastructure network based on spatial prioritization

The destruction of the ecological system caused by urban expansion has led to the environmental deterioration,cities have become increasingly vulnerable.In this study,six districts and counties along the Yellow River in Zhengzhou were selected as the study area.First,green infrastructure elements were extracted by morphological spatial pattern analysis.Then,outside the urban areas,we used connectivity analysis to evaluate the importance of core areas,adopted minimum cumulative resistance model to extract potential corridors,and identified the important corridors by using the gravity model.Finally,in the urban areas,we set up an evaluation system to assess the demands for ecosystem services.The results showed that:(1)Seven landscape types of green infrastructure be identified in study area.(2)There are 17 vital cores,136 potential corridors,and 24 vital corridors outside the urban areas.(3)The blocks with high demand for ecosystem services are mostly concentrated in the old blocks with dense populations and poor infrastructure,and there are 5 blocks with comprehensive high-demand.Based on identified importance for green infrastructure land space,and high-demand level for ecosystem services areas in this study,a green infrastructure net plan was proposed based on spatial conservation prioritisation.